Sheep blowfly vaccine shows promise in the lab but fails in field

Research is battling to find a vaccine to control flystrike but early tests keep falling at the first hurdle. Here’s what the next move is.

Flystrike vaccines that work in a laboratory are failing to produce the same results on sheep.

But researchers are hopeful they can find ways to make two candidate vaccines work more effectively out in the field.

CSIRO researcher Dr Tony Vuocolo said there had been a resurgence in work on a flystrike vaccine after it stalled in about 2000.

“We did some great foundation work over a period of 10 years from the mid 80s to middle of 2000 and then the work stopped,” Dr Vuocolo said.

“We had really come as far as we could with the technologies that were available but we are in a position now where there is a convergence of technology and capability and knowledge.

“It was time to give the vaccine another good go.”

Dr Vuocolo said producing a vaccine was “like an assault on Mount Everest”.

“We need to establish a really good base camp of understanding and then plan your assault as you are moving up,” he said.

Australian Wool Innovation researchers make progress in mapping the gene of the blowfly, which causes flystrike.

“I am happy to say we are past base camp and not quite reached Hillary's step yet but we are well on our way.”

The research is now at a point where many vaccines are raising strong immune responses in sheep in laboratory trials and having a real effect on survivability of maggots.

But it is a huge step to move onto later stages Dr Vuocolo said.

“A maggot is like a World War 1 tank — it’s armour plated and a really difficult thing to target,” he said.

The research has shown the best target area is the maggot’s gut.

Two vaccines have been developed — one that uses proteins extracted from maggots to produce a vaccine and the other is a molecular approach where key proteins are put into cells and then into a vaccine.

There were more than 50 prototype vaccines developed during the past three years, which have been narrowed down to two lead prototypes.

In the lab, those vaccines caused maggot growth to be stunted, dying or moribund and there was a 75 per cent reduction in weights and growth rates.

But that was not replicated when the trials moved outside the lab with only a 20 per cent reduction on sheep.

“The biggest hurdle at the moment, (is working out) what we can do to amplify the immune response on the sheep to be much more resilient to larvae,” Dr Vuocolo said.

“We are pretty early into the project and while I would like to be able to tell you there will be a vaccine in the next couple of years, really that is not right.”

A spokesman for Australian Wool Innovation said it had invested $2.85 million to support the development of a flystrike vaccine.